Hi Bill,
I tuned up my 10-50-10 EWEs by listening to BCB stations that
are at least 100 miles distant. I used a battery operated
"communications receiver" connected to the transmission
line transformer with a short length of coax and I connected the
headphones to the radio with a long length of "bell" (twisted pair)
wire while adjusting the terminating resistor. If you try that,
use a "long" length of the "bell" wire and avoid placing it directly
under the horizontal part of the EWE....off to the side somewhere
is best....one could also use a audio level meter and speaker,
and view the meter with binoculars while adjusting. One could
also use a long length of coax and have the receiver right at the
null adjustment site.
To tune the directions I wanted to null out, I first got a list of
AM stations and the Lat/Lon of their transmitters, power level,
etc all within 250 miles of my QTH. Then I selected various
stations that were within +- 30 degree arc off the BACK of my
EWEs. With a list of "good" stations, I made sure I could first
hear the chosen stations on my radio connected to the
main transmitting antenna, deleting those that I couldn't hear.
So, armed with a good station list and their directions I made
the null adjustments and in most cases I was able to completely
null out a station received from the back side. The preferred
stations were on the upper part of the AM BC band.
I found a station list on a FCC web site quite some time ago
and have since lost the web address. Try a search on Google
and see what comes up, or ask some fellow top banders.
If you have difficulty getting a null you might try a wide range
carbon pot (if you haven't tried that already), say 2K, and
make sure that your EWE has good (and stable) ground
connections.
73,
Charlie, N0TT
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